1. Field of the Invention
The present invention relates generally to processing of hydrogen and relates specifically to a method for storing and retrieving hydrogen for use in consumer applications.
2. Description of the Related Art
Gaseous hydrogen as a fuel for combustion or for oxidation has many advantages. In a combustion process, hydrogen bums cleanly and without the polluting emissions of burning hydrocarbons. Additionally, hydrogen may be used in fuel cells to produce an electrical current, providing electricity for consumer use or for powering motors for use in automobiles.
Hydrogen is available in storage tanks as a compressed gas. However, the amount of hydrogen that can safely stored in these tanks is limited. Also, gaseous hydrogen is highly flammable, and the small size of hydrogen atoms makes controlling leaks difficult.
Liquid hydrogen is used in the aerospace industry to provide a larger amount of hydrogen for a given storage volume, but this is only practical for limited, high-cost applications. Storage tanks and plumbing have to be specially designed to withstand and maintain the extreme temperatures of liquid hydrogen. Also, special handling is required that would not be conducive to a consumer product.
Carbon nanotubes are three-dimensional, tube-shaped structures formed by carbon atoms arranged in hexagonal patterns. Nanotubes may have single-wall thickness or may comprise multiple nested nanotubes. It is known that carbon nanotubes have an affinity for hydrogen and can store hydrogen atoms in pores on the surface of the tubes and within the tube structures, allowing for more hydrogen atoms to be stored in a volume than can be stored with the hydrogen as a compressed gas.
A method is provided for delivering gaseous hydrogen to end users, the hydrogen being delivered in reusable storage tanks containing a plurality of carbon nanotubes. Liquid hydrogen is introduced into the tank, and the nanotubes absorb the hydrogen. The tanks are then warmed to normal temperatures and distributed to end-user. The tanks are connected to the end-user system and are preferably installed within an airtight enclosure, which may have an inert atmosphere. Alternatively, an inerting system monitors the air within the enclosure for free hydrogen and can release an inerting gas if free hydrogen is detected. The hydrogen is selectively released by heating the storage tank or by injecting a catalyst into the tank. When the usable hydrogen is depleted, the tank is retrieved from the end user for refurbishment and refilling.